Refinement of Thermodynamic Parameters of the Mg24Y5, W and H Phases in the Mg-Zn-Y System

The Mg-Zn-Y alloy shows excellent mechanical properties which can be achieved by combining LPSO phase (known as X phase) and an icosahedral quasicrystal phase (I and Z phases) in Mg solid solution (α phase). Thermodynamic data for the binary/ternary compounds Mg24Y5, X, W and H have to be critically assessed to obtain accurate information of three-phase equilibrium in order to understand equilibria among these phases. In this research, we focused on developing CALPHAD (CALculation of PHAse Diagrams) thermodynamic database to evaluate phase diagrams for the Mg-Zn-Y system. Especially thermodynamic models for the Mg24Y5, W and H phases have been determined based on crystallographic data. Then thermodynamic parameters have been assessed to yield experimental data from EPMA/WDS, SEM, TEM and X-Ray diffraction.